slow shutdown and very slow boot-up.

These slow startup/Shutdown problems mostly occur, if one of the background application conflicts with the startup/shutdown process or that it takes more resource to load/unload.

Best option would be to open the System Configuration utility and try to Disable all Startup programs and check if it solves the problem. If yes, then one of the background application is the culprit.

To disable the startup/background applications,

Click Start - Run, type MSCONFIG and enter.
Click the Startup tab and click 'Disable All' & click Apply & Ok, Restart the computer.

NOTE: Disabled appl. will still be accessible from Start - All Programs when necessary.

This should help. Also, try to use Ad-aware to find and delete adware/spyware programs that may be the cause of this problem.

Ad-Aware can be downloaded from,

http://www.lavasoftusa.com/software/adaware/

This should help.